#include<stdio.h>

int main()
{
    int a=21,i;
    printf("Game begin:\n");
    while(a>0){
        do{
            printf("How many sticks do you wish to take (1~%d)?",a>4?4:a);
            scanf("%d",&i);
        }while(i>4||i<1||i>a);
        if(a-i>0) printf(" %d sticks left in the pile.\n",a-i);
        if((a-i)<=0){
            printf(" You have taken the last sticks. \n");
            printf(" ***you lost! \n Game over. \n");
            break;
        }
        else
        printf(" Computer take %d sticks. \n",5-i);
        a-=5;
        printf(" %d sticks left in the p...\n",a);
    }
}